Lubricant



Patented Nov. 7, 1939 UNITED STATES PATENT OFFICE LUBRICANT No Drawing. Application June 25, 1987, SerialNo. 150,324

14 Claims.

This invention relates to naphthenyl esters of acids of phosphorus, some of which are new chemical compounds, the methods of preparing the same, and particularly to the use of such esters in lubricating oils to provide lubricants having improved properties.

Aliphatic and aromatic esters of ortho-phosphoric acids are known. Such esters have been employed as plasticizers in molding and coating compositions, particularly in those containing cellulose ethers' and esters. They have also been proposed for use as textile lubricants and as assistants for-extreme pressure lubricants and for many other purposes. Such prior known phosphates, particularly the higher aliphatic phosphates, have the disadvantage that, under certain conditions, they tend to exude from the compositions containing them.

The advantages of a high pressure lubricant become apparent when the present trend in design of automotive and other machine parts, and the increased strength of metal parts, due to the use of alloy steels, is considered. The pressures ordinarily found in well lubricated journal bearings do not exceed 2,000 lbs/sq. in. and for conditions such'as this, a film of heavy oil can be expected to remain between the rubbing surfaces. When gears are considered, where the contact between surfaces is of very small width, the bearing pressures often reach values as high as 25,000 lbs/sq. in. Under such extreme pressure, it is unlikely that any oil or grease can be obtained which will be viscous enough to prevent metallic contact. The result of the lack. of a lubricating film between the rubbing surfaces results in scoring and scuffing of the gears.-

Failure to maintain lubricant films on idle bearing surfaces is now well recognized as the cause of 70 to 80% of the wear occurring on 40 cylinder walls of automotive and other internal combustion engines. When an engine is stopped, the oil film on the vertical surfaces soon drains off and, when the machine is again started, an appreciable time elapses before the circulation provides oil for the formation of new lubricant films. An a"sistant which, when added to the motor oil, will prevent the separation of the oil film from the metal should prevent a large part of the wear now occurring.

Recently'new bearing metals have been proposed for use in automobiles such as those composed of cadmium-silver alloys, cadmium-nickel alloys and copper-lead alloys supported upon steel backings. These new alloys have many advantages over the older type, but are in general subject 'to destructive agencies of a corrosive nature. The morehighly refined oils, particularly those-obtained by solvent refining, appear to be particularly corrosive toward such new alloys.

Various agents have been added to oils to improve their properties. Among such agents which have been used are sulfur, sulfur-containing compounds, metal soaps, halogen compounds and the like. Some of these agents, such as the sulfur and halogen compounds, greatly improve the lubricating properties of the oil whereas others, such as the metal soaps, have been of little value for this purpose. Some of such agents are corrosive or give rise to corrosive products, and are therefore objectionable. Many of such agents tend to increase or accelerate sludgeformation in the oils to an objectionable extent, and are objectionable for this reason.

It is an object of the present invention to provide new materials for addition to lubricating oils for improving their properties. A further object is to provide improved lubricating oils. A still further object is to provide a method for preparing improved lubricants. Other objects are to provide new compositions of matter and to advance the art. Still other .objects will appear hereinafter.

The above objects may be accomplished in accordance with my invention which comprises incorporating in lubricating oils, particularly petroleum lubricating oils, naphthenyl esters of the acids of phosphorus and mixtures of such esters, some of which esters are new chemical compounds. I preferably employ the naphthenyl esters of phosphorus acids;' in other words, the naphthenyl phosphites and naphthenyl' thiophosphites. These esters may, in general, be prepared by any of the methods well known to the art. I

By the term naphthenyl alcohols as employed herein and in the claims, I mean the alcohols which are obtainable by the carboxylic reduction of naphthenic acids and their esters. These alcohols contain at least six carbon atoms and may contain as many'as twenty or more carbon atoms. These naphthenyl alcohols contain the hydroxyl group in a side chain as distinguished from the cycloallphatic alcohols in which thehyclroxyl group is attached to a carbon of the cyclic nucleus. A naphthenylradical as employed hereinafter and in the claims will be understood to mean a radical derivable from such naphthenyl alcohols. The naphthenyl. esters of my invention are those .obtainable by esterifying such naphthenyl alcoh Til By an acid of phosphorus as employed herein and in the claims,.I intend to include the various phosphoric and phosphorous acids such as the ortho, meta,'pyro and hypo acids together withthe corresponding thio acids in which one or more of the oxygens are replaced by sulphur atoms. Among the esterifying derivatives of acids of phosphorus, the following are the most common:

The process of making naphthenyl esters of ortho-phosphoric acid may be'carried out by placing one or more of the naphthenyl alcohols alone or dissolved in a suitable solvent, such as benzene, toluene, chloroform and the like, in a vessel connected with a reflux condenser. The material in the vessel is warmed to the desired temperature, preferably 30 to 100 C., under reduced pressure and phosphorus oxychloride is then gradually admitted in liquid or vapor form. The reaction is carried to completion under reduced pressure in the heated vessel and the hydrogen chloride formed is continuously removed. The resulting phosphates may be purified by distillation under reduced pressure. The resulting product comprises the mono-, di-,' or tri-naphtheny1 phosphate, depending upon the proportion of alcohol employed. When more than one molecular proportion of the alcohol is employed and the alcohol comprises a mixture of naphthenyl alcohols, the resulting product is a mixture of phosphates which apparently contains a substantial proportion of mixed phosphates each of which contains two or more different naphthenyl radicals.

The esters of ortho-phospho'ric acid may also be obtained by heating the naphthenyl alcohol on a 'water bath and then adding phosphorus pentachloride thereto, slowly. The product may be washed with water and dried in vacuo.

The esters of ortho-phosphoric acid may also be obtained by dissolving a mixture of the alcohols in ether or other suitable solvent, such as pyridine or other tertiary base, and then heating with phosphorus pentcxide under a reflux condenser. When ether is used as the solvent, the

. ester separates on cooling. 'i i hen pyridine and like compounds are used, the solvent removed.

b distillation, the product Washed with water and dried by heating under cecl The esters may also be pre responding alkoxides and then reacting the allo amides with phosphorus oitychloride or the like An alternative procedure comprises first pre, ing the naphthenyl iodidesor other halides and then reacting the halide with the silver salt of pyrophosphoric, metaphosphoric, orthophosphoric or other acid of phosphorusto obtain the neutral or acid esters, depending upon the proportions employed.

If it is desired to obtain pure mixed esters of ortho phosphoric acid, it will be desirable to react one molecular proportion of phosphorus oxychloride with one or two molecular proportions of the naphthenyl alcohol. The resulting product is principally the chloride 01 the monoor dinaphthenyl phosphates. After removal of the hydrogen chloride, a second alcohol or mixture of alcohols, different from the first, an alkali metal phenolate or a free phenol in the presence of a tertiary base is added, preferably in excess. By this method, the pure mixed neutral or acid esters are obtained.

Catalysts such as copper powder or a metallic chloride may be added to the reaction liquid in order to facilitate the splitting off of the hydrogen chloride. Also, the degree of reduced pressure employed may vary'within wide limits depending upon the desire of the operator and the materials being treated.

The esters of the other acids of phosphorus may be prepared in similar manner to the methods disclosed above by substituting the proper esterifying derivative for the phosphorus oxychloride and the like, disclosed above. For example, when phosphorus trichloride is employed, the phosphites will be produced. When phosphor-us sulphochloride is employed, the resulting products will be the monothio ortho-phosphates. When phosphorus pentasulfide is employed, the dithio ortho-phosphates result. When phosphorus trisulpho tetra bromide is employed, the corresponding trithio pyro-phosphates will be produced. The metaphosphates may be obtained by treating the neutral ortho-phosphates with concentrated sulphuric acid.

Esters of thio acids of phosphorus may be produced by treating the naphthenyl thio alcohols with an estcrifying derivative of phosphorus. The resulting compounds will generally have the naphthenyl radical attached to the phosphorus through a. sulphur atom. These esters may be called thio esters of the acids of phosphorus to distinguish them from the esters of the thio-acids in which the naphthenyl radical is attached to the phosphorus through an oxygen atom.

When the neutral esters are treated with alkali, the alkali metal salt of the dinaphthenyl ester is obtained. These salts may be prepared by boiling one part by Weight of the neutral phosphate with 8 parts by weight of sodium hydroxide dissolved in 192 parts by weight of water for two hours. These salts are soluble or dispersible in Water. The sodium salts of the mixed dinapnthenyl phosphates can be employed to emulsii'y a mineral oil in a large amount of water to oba tam an emulsion which can be diluted indefinite- 13 with Water.

The neutral napthenyl esters can alsobe hy drolyzed by cooking with an acid such as hydrachloric acid to yield mixtures of the mononaph thenyl and dinaphthenyl phosphates.

While'the sodium salts of the acid esters of my invention are soluble in Water, the salts ob taincd with organic bases, such as triethanolamine or methyl glucamine, are even more soluble. These various salts also form a part of my in vention.

in order more clearly to illustrate my invention and the preferred modes of preparing my new compounds, the following examples are given:

Example I culatedfrom analytical determinations of the saponification number of the ethyl naphthenates 7 c ron c weight of this mixture was mixed with 100 parts of benzene. 8 parts by weight of phosphorus oxychloride was then added slowly. The mixture was placed in a glass vessel attached to a reflux condenser and heated at the reflux temperature under a slight vacuum for 20. hours. The slight vacuum served to assist in the removal of the hydrogen chloride which was formed. Thebenzenesolution was-then washed withwarm water until'neutr'al and the benzene evaporated. The mixture was then steam distilled until no more oily liquid came over. The solution in the steam distillation flask was then extracted with ben- Zeus and the layers separated. The benzene layer was then evaporated on a steam bathleaving dinaphthenyl phosphate; The last traces of benzene were removed by heating under reduced pressure. The productwas a light yellow viscous liquid, soluble in aromatic hydrocarbons and insoluble inwater. Determination or the phosphorus content indicated that the product was the expected dinaphthenyl phosphates.

v Example 2 having an indicated molecular weight of 169, as

I 160 C. at -1 mm. and having an average molecucalculated from analytical determinations of hydroxyl number, was obtained. 100- parts by weight of this mixture was mixed with'200 parts of benzene and 32 parts of phosphorus oxychloride was then added slowly. The mixture was placed in a glass'vessel attached to a reflux condenser and allowed to stand at room temperature for 3 hours under a slight vacuum. The mixture was then heated in a steam bath over night under a slight vacuum. The reaction mixture was then poured into an excess of dilute sodium carbonate solution and the mixture steam distilled until there was no further detectable distillation of ,oil'y materials. The residue in the steam distiblation flask wasthen extracted with benishe and thoroughly washed with'water. The benzene solution was dried by distillation of the benzene,

the last traces of the benzene being' removed under reduced pressure. The product was a, light yellow" viscous liquid, soluble in aromatic hydrocarbons and-insoluble in water. Determination of the phosphorus content indicated the product to be dlnaphthenyl phosphates.

(- Example 3 by sodium reduction. This produced a mixture of naphthenyl alcoholsboiling betweenl30 and lar weight -of'274 as calculated from an analytical determination of the hydroxyl number. Thirty-seven and five-tenths parts by weight this mixture was mixed with 100 parts oi-toluene. Seven parts by weight of phosphorus oxychloride I was added slowly. The mixture was placed in a glass vessel attached to a reflux condenser and heated gently'on a steam bath under slightvacunm to remove liberated hydrogen chloride. After heating for 24- hours, 3.5 parts of phosphorus oxychloridewas added, inorder to have present sufflcient phosphorus oxychloride so that only the dinaphthenyl phosphate would be formed: ,The

.. mixture was heated under slight vacuum in the steam bath for threeaddltional hours. Benzene was added to the reaction mixture and the bon zene solution thoroughly with dilute sodium carbonate solution. Very stable emulsions Dilute hydrochloric acid was then added to decompose the sodium salt and the solution washed thoroughly with water.. The benzene layer was separated and the benzene was removed under vacuum en the steam bath. The product was a light yellow colored v'er'y viscous liquid, soluble in aromatic hyd ocarbons and insoluble in water. Determination of the phosphorus content ndicated "the product to be dinaphthenyl orthophosphates. This m'aterial'was added to an oil in"2% concentration and the resulting lubricant withstoodja load of, about 28,000 lbs/sq; in.. when tested 'on the .Almedmachine,

While the phosphates to some extent reduce the tendency of lubricating oils to corrode alloy bearing metals such as cadmium-silver,

copper-lead "and cadmium-nickel alloys, I have found that thenaphthenyl phosphites and naph thenyl tliiophosphit'es are" particularly eflective for retarding corrosion for suchbearing, alloys by mentor ng oils. The following. additional examples illustrate this' desirable property:

Example 4 tation, a, solution of 6.8 m phosphorus trichloridein 50 cc. benzen The reaction mixture was agitated 1 hour at 25 C. and subsequently heated 1 hour on a steam bath. Nter' hilling. the s lutionwas filtered-to remove the solid pyridine hydrochloride, shaken for minutes with 20 gms. sodium carbonatemmohydrate to complete the removal of chlorine -oontaininegcompounds,

the'solvent removed under reduced pressure; A clear liquid residue was obtained,

filtered, and

w shin to whichunon analysis yielded .tne=rouowiiig data: phosphorus iiound), 3.45%:

nhosp bm alculated). M593; Kn, 1.4965. I TheIeiiectoi this matarlalson the film strength (if-an SAE 30 oil was determined on the Almen machine with the following results:

Load supported real in. Oil alone 3,000 0il+1% naphthcnylj phosphite 28, 000

The efiect ofthis material in inhibitin the corrosionof a copper-lead alloy bearing and a cadmium-silver alloy hearing was determined on an SAE 30 oil as follows:

Fiity grams of oil containing 0.5% byweight oithe naphthenyl phosphite were placed in 125 cc. lenmeyer flasks'each equipped with a l capillary inlet tube throughwhich moistv air was at the rate of 2 to 3 bibbles per second. Strips cut from the hearings were suspended in the flasks in a position such that half of the suriace-oi. strip was immersed in the oil halt exposed to the vapors. The flask; and contents were placed in an oil bath at 170 C. for hours. A control test was run si-' multaneously. At the end the test, the bearing strips were removed. washed th chloroform. and

acetone, and weighed. The data obtained or as follows:

, loss per 16 gms.

' form e Copper- Cadmiumlead alloy silver alloy Oil alone m. 100 102 Oii+0.5% naphthenyl phosphite 5 Example A solution of 23 gms. naphthenyl mercaptans. having an average molecular weight of .180, and gms. pyridine was prepared in 100 cc. benzene.

..To this was added, slowly and with vigorous agitation, a solution of 5.5 gms. phosphorus trichloride in 50 cc. benzene. The reaction mixture was agitated 1 hour at 25 C. and subsequently heated 1 hour on a steam bath. After chilling, the solution was filtered to remove the solid pyridine hydrochloride, shaken for 30 minutes with sodium bicarbonate to complete the removal of chlorine-containing compounds, filtered, and the solvent removed under reduced pressure. A clear liquid residue was obtained weighing 21 gms. Upon analysis this yielded the following.

data: phosphorus (found), 5.28%; phosphorus (calculated), 5.45%; sulfur (found), 15.49%; sulfur (calculated), 16.9%; No", 1.5269. Y

The effect of this material on the film strength of an SAE 30 oil was determined on the Almen machine with the following results:

Load support Lbs/sq. m. 011 alone 3, 000 0il+1% naphthenyl trithiophosphite 24, OQO

' The effect of this material in inhibiting the corrosion of bearings lined with a silver-cadmium alloy and with a copper-lead alloy, was deter mined on an SAE 30 oil as follows:

Fifty grams of oil containing 0.5% by weight of the naphthenyl tri'thiophosphite were placed inl25 cc. Erlenmeyer flasks each equipped with a 1 mm. capillary inlet tube through which moist air was passing at the rate of 2 to 3 bubblesper second. Strips cut" from a silver-cadmium alloy bearing and a copper-lead alloy bearing were suspended in the flasksin such a fashion that half the surface of each strip was immersed in the oil and half exposed to the vapors. The flasks and contents were placed in an oil bath at 170" C. for 50 hours; A control test was run simultaneously. At the end of the test, the bearing strips were removed, washed with chloroform and acetone, and weighed. The data obtained are as follows:

' Mg. loss per 10 grams Ior- . Silver- Cop load alloy "213? on aim s5. 5 244.1

l+0.5% noththenyl trlthlophosphite. 4.9 0

I have found that the naphthenyl phosphites and the naphthenyl thiophosphites have a further' advantage over the prior art compounds in that they have greatly improved sludging characteristics over similar compounds proposed in the prior art. They do not tend to cause the oil to form sludge or accelerate the formation of sludge in the oil to the extent that similar compounds heretofore proposed do. When the corrosion tests disclosed in Examples. 4 and En were run, the tendency of the treated oils to form sludge was also tested. The results of such tests are given in the following table: 1'

Concen 'lemper- Mg. sludge if tration, Length Compound gg of test atltiergtoi per gil gms.

weig

r Hours *C. Naghthenyi phosp its 0.5 50 '170 17.5 Naphthenyl trithiophosphlte .l 0. 5 50 170 l. 6 Triphenylphosphite (commcrcialgrade)- 0.5 50 170 23.1

The sludge values were determined by diluting 10 gms. of the oil to a volume of 100 cc. with a highly refined petroleum naphtha, allowing the solution to stand at 0 C. forone hour, filtering the solution on a weighed Gooch crucible, and weighing the collected sludge.

From the above tests, it will be apparent that the oil containing the phosphites and thiophosphites of my invention had much less tendency toward the formation of sludge than triphenyl phosphite, which is a representative of similar types of compounds which have been proposed for addition to lubricating oils.

The preferred esters of the acids of phosphorus of my invention are derived from naphthenyl alcohols obtained by hydrogenation or sodium reduction of derivatives of naphthenic acids from petroleum, and particularly the esters of the phosphorous acids. However,.I intend to include 'within the scope of my invention the mixed esters such as dinaphthenyl ethyl ortho-phosphate,

dinaphthenyl cresyl ortho-phosphate, dinaphthenyl 9,10-octadecenyl ortho-phosphate, dinaphthenyl dodecyl ortho-phosphate, acid naphthenyl dodecyl ortho-phosphate, acid naphthenyl ethyl ortho-phosphate, acid naphthenyl cresyl orthophosphate, acid naphthenyl tetradecyl orthophosphate, acid naphthenyl 9,10-octadecenyl ortho-phosphate, acid naphthenyl phenyl orthophosphate and similar compounds. These mixed phosphates may be obtained -by esterifying a mixture comprising at least one molecular proportion of the naphthenyl alcohols and one molecular proportion of a, different alcohol or a phenol. .They may also be obtained'by first esterifying the naphthenyl alcohols and then reacting with the other alcohol or phenol. Alternatively the other alcohol or phenol may be first esterified and then reacted with the naphthenyl alcohols.

The neutral esters of my invention may be employed as plasticizers in molding and coating compositions, particularly those comprising cellulose ethers, such as the benzyl ethers, and cellulose esters, such as the nitrate and acetate. The acid phosphates and their alkali metal salts such as sodium and potassium and the ammonium and amine salts are useful as wetting agents, detergents, textile lubricants and the like. The acid phosphates are also useful as lubricant assistants for extreme pressure lubricants. For example, when 2% of dinaphthenyl phosphate, such as that obtained in accordance with Example 3, is added to a medium viscosity mineral oil,-

' 5 tion of the phosphites and thiophosphites and SAE 30, and dissolved therein by heating, the

oil-was able to maintain a lubricant film under extreme high pressure which it would ordinarily not withstand, and had a much higher degree of 'oiliness.

The method of testing my compounds was that devised by J. O. Almen (Oil and Gas Journal, 30, 109, 1931). This method consists of running a 4" diameter drill rod between two halves of a split bushing which is maintained stationary. The load on the bushing is controllable and provison is made for measuring the torque developed by the friction of the lubricant film. A hydraulic system forincreasing the loading on the bushing until the oil film breaks and the metal seizes is provided. The rubbing speed is about 50 feet per minute and the method of loading is gradual, one weight being added to the loading lever each ten seconds. Each weight added to the loading lever increases the pressure on the bushing by about 125 lbs. The machine provides for 'beam loadings up to 20 weights which corresponds to a pressure of 20,000 lbs/sq. in. on the full projected area of the drill rod. The-bear-- ing surface of the bushing is cut to a diameter 0.007 inch larger than the drill rod so that, before any wear occurs, the actual'bearing surface is a line. As wear occurs, the bearing surface widens but seldom covers the bushing. After a test, thewidth of the bearing scar can be measured and an approximate value for the actual bearing pressure obtained. The valves given in the preceding examples represent the calculated actual bearing, pressures which were reached in the tests without failure of the film. These valof paramn oil will withstand a pressure of only '3 to 5,000 lbs/sq. in. When an oil containing sulfur is tested by the same method, such oil will show a film strength of about 20,000 lbs/sq.

in. and will give a torque reading of over 4.0 lbs.

ft. at this load.

This application is inpart a continuation of my copending application Serial No. 11,809, filed March 19, 1935, for Esters of the acids of phosphorus. In such copending application. I have disclosed the phosphates both generically and specifically, and the phosphites and thiophosphites generally. Also, in such copending application, I have disclosed that these compounds are useful additions tolubricating oils for producing extreme pressure lubricants. The present application includes a description of the preparathe results of tests of lubricating oils containing such compounds.

While I have disclosed the preferred embodiments of my invention and the preferred modes of carrying the same into effect, it will be read- K ily apparent to those skilled in the art. that many modifications may be made therein without departing from the spirit of my invention. Accordingly, the scope of my invention is to be limitedvsolely by the appended claims construed as broadly as is permissible in view of the prior art.

I claim:

1. A lubricant comprising a lubricating oil having incorporated therein an ester of an acid of phosphorus containing at least one naphthenyl radical.

2. A lubricant comprising a lubricating oil having incorporated therein an ester of a phosphorous acid containing at least one naphthenyl radical.

3. A lubricant comprising. a lubricating oil having incorporated therein a naphthenyl phosphite.

4. A lubricant comprising a lubricating oil having incorporated therein a naphthenyl'thidphosphite.

5. A lubricant comprising a lubricating oil having incorporated therein'a naphthenyl trithicphosphite.

6. A lubricant comprising a lubricating oil having incorporated thereintrinaphthenyl trithiophosphite.

7. A lubricant comprising a lubricating oil having incorporated therein an acid-ester of an ortho-phosphoric acid containing at least one naphthenyl radical.

8. A lubricant comprising a lubricating oil having incorporated therein dinaphthenyl phosphate.

9. A lubricant comprising a lubricating oil having incorporated therein a mixture of naphthenyl esters of an acid of phosphorus obtainable by .reacting an esterifying derivative of an acid of phosphorus with at least one molecular proportion of a mixture of naphthenyl alcohols.

10. A lubricant comprising a lubricating oil having incorporated therein a mixture of naphthenyl esters of a phosphorous acid obtainable by reacting an esterifying derivative of a phos-' phorous acid with at least one molecular proportion of a mixture of naphthenyl alcohols.

11. A lubricant comprising a lubricating oil having incorporated therein a mixture of naphthenyl esters of a thiophosphorous acid obtainable by reacting an esterifying derivative of a phosphorous acid with at least one molecular proportion of a mixture of naphthenyl mercaptans.

12. A lubricant comprising a lubricating oil having incorporated therein a mixture of acid esters of an ortho-phosphoric acid obtainable by 'an esterifying derivative of phosphorous acid with three molecular proportions of a mixture of naphthenyl mercaptans.

PAUL LAWRENCE SALZBERG. 

